I mentioned this on the python-dev list [1] originally as a +1 to someone else suggesting the idea [2]. It also came up in a response to my post that I can't seem to find in the archives, so I've quoted it below [3].
As the subject says, the idea would be to add a "+" and "+=" operator to dict that would provide the following behavior:
>>> {'x': 1, 'y': 2} + {'z': 3}
{'x': 1, 'y': 2, 'z': 3}
With the only potentially non obvious case I can see then is when there are duplicate keys, in which case the syntax could just be defined that last setter wins, e.g.:
>>> {'x': 1, 'y': 2} + {'x': 3}
{'x': 3, 'y': 2}
Which is analogous to the example:
>>> new_dict = dict1.copy()
>>> new_dict.update(dict2)
With "+=" then essentially ending up being an alias for ``dict.update(...)``.
I'd be happy to champion this as a PEP if the feedback / public opinion heads in that direction.